Plankton: critical little critters

Plankton are responsible for half the air we breathe, and are critical to the marine food web. Our research into plankton tells us about the changing nature of the ocean.

The challenge

Improving understanding of the marine environment

Oceans are the home of plankton, the species-rich microscopic life-blood of the marine ecosystem, responsible for fisheries production, nutrient cycling, gas production and climate regulation.

Every day in the ocean, oxygen-producing plankton, called phytoplankton, perform nearly half of the photosynthesis on Earth.

The animal plankton, zooplankton, graze phytoplankton, and is plentiful in the sea. Its abundance, growth, timing and composition determine the ocean's carrying capacity. This means how much plankton present in the ocean controls the numbers of fish, squid, jellyfish, mammals, seabirds, sea turtles, crabs, shellfish and other marine creatures.

Plankton influence the pace and extent of climate change. They produce chemicals that assist in the formation of clouds, plus through photosynthesis transport carbon to the deep ocean.

Plankton also impact human health, producing toxins from large harmful algal blooms or red tides, which can cause contamination of human food.

Plankton is an important ecological indicator, and understanding how its abundance and the species present are changing is critical to predicting the future of our oceans.

Sampling zooplankton off North Stradbroke Island National Reference Station

Our response

Using plankton as an ecological indicator

We are working on plankton to better understand the challenges facing the marine ecosystem.

This is made possible through the Australian Integrated Marine Observing System (IMOS), a national ocean observing system measuring the physical, chemical and biological environment.

Plankton observations within IMOS are provided by the Australian Continuous Plankton Recorder Survey and the National Reference Stations program.

Using this plankton data we are able to study climate change, ocean acidification, productivity of fisheries, biodiversity and ecosystem health.

Data collected through IMOS is fed into our ecosystem models, which give us a clearer picture of what future oceans may look like, and how we can better manage our marine environment now.

We are also using this data to contribute to ecosystem assessment reports, such as the recent State of Environment Report 2016 , in marine bioregional planning, and for forecasting venomous jellyfish occurrence.

The results

Changing plankton distributions and species mix

Using IMOS plankton data collected regularly over the past 10 years we have discovered shifting patterns in plankton populations around Australia. We have been able to compare this data with historic plankton data collected by researchers in the past.

We have seen normally tropical populations of copepods, a tiny shrimp-like zooplankton, migrate south to Tasmania, displacing cold-water species. This is in response to warming oceans around Tasmania and a southward shift of the East Australian Current. The smaller tropical planktons are not as good a source of food for fish as the displaced large cool-water species.

We have also gathered evidence that the East Australian Current has transported south harmful and nuisance plankton species, such as Noctiluca, a species that can cause red tides, and that has been implicated in the decline of fisheries in the Indian Ocean.

We are tracking plankton that have calcium carbonate (limestone) shells (e.g. young of mussels and clams, sea butterflies known as pteropods) that could be detrimentally affected by our oceans becoming more acidic due to more CO2 in the atmosphere. So far our data show that there is no decline in abundance of these shelled plankton species, which is good news, but we will continue our monitoring into the future.

Unusual biodiversity records have also been found across Australia, including species identified in our waters for the first time. Some of these could be new here because of climate change, but it is probably more likely they have been overlooked in the past. Documenting the biodiversity present around Australia forms an important baseline for assessing future changes.

Jellyfish are an understudied zooplankton group, and we are working to understand the distribution and abundance of species, particularly poisonous ones such as Irukandji.

Our research confirms that without plankton, the Earth would be warmer and devoid of large fish and charismatic marine animals.

Rhincalanus copepod. Large copepod plankton that is important as food for fish

Rhincalanus copepod. Large copepod plankton that is important as food for fish

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